Estimating Agricultural Groundwater Withdrawals with Energy Data

Agricultural water use is the leading cause of groundwater overdraft in California. However, agencies tasked with managing groundwater resources do not have access to accurate and reliable measurements of groundwater extraction. Previous studies identified a relationship between pump energy consumption and groundwater extraction and indicated that the efficiency lift method (ELM) can produce reliable estimates of groundwater extraction if based on reliable data. Recent advances in the availability of electricity and pump operating condition data have made the ELM viable for estimating large-scale groundwater extraction. This study considered the feasibility of using the ELM to estimate groundwater extractions from both individual wells and larger areas and identified the best data sources available for such estimates. Researchers found mean error rates of 5% at the individual well level and 3.3% for collections of wells when using the most specific data sources available, such as pump test reports and spatial groundwater level datasets. This research suggests that the ELM is a reasonable approach for estimating groundwater extraction on a large scale.

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Residential Solar Water Heating: California Adopters and their Experiences

Solar water heating provides domestic hot water with lower greenhouse gas emissions compared to more typical natural-gas water heating. Solar water heating has a long history, particularly in places where the climate is favorable, such as California where state-backed incentive programs have been successful in creating small bursts of adoption. However, widespread adoption of solar water heating has not occurred in California despite these conditions. This research surveyed 227 single-family households with solar water heating across the state of California to understand their motivations and experiences, and draw implications regarding barriers to adoption. The survey explored households’ experiences across five stages of adoption, as outlined in Rogers’ Diffusion of Innovation theory: Knowledge, Persuasion, Decision, Implementation, and Confirmation. Findings revealed challenges at each stage. Most notably, prevalent disappointment in lower-than-expected energy and bill savings (31%) and high rates of technical problems (41%) appear to be the most significant issues.

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Low-Cost, Large-Diameter Shallow Ground Loops for Ground-Coupled Heat Pumps

This project developed and validated modeling tools for simulating a ground heat exchanger technology that provides a less expensive method for implementing ground-source heat pumps and significantly reduces energy use in many California climate zones, furthering attainment of California’s energy goals. It is well documented that properly sized and installed ground-source heat pumps enjoy higher system efficiencies than conventional air-source systems by exchanging heat with the ground rather than with ambient air. Ambient air temperatures are hottest when cooling is most required and coldest when heating is most required. Exchanging heat with the ground reduces the temperature extremes and improves heat pump performance.

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